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Date May 2015 Marks available 1 Reference code 15M.3.HL.TZ1.2
Level Higher level Paper Paper 3 Time zone Time zone 1
Command term Define Question number 2 Adapted from N/A

Question

Outline the endosymbiotic theory.

[2]
b.

 Define gene pool.

[1]
c (ii).

Markscheme

a. mitochondria/chloroplasts were once (independent) prokaryotes;
b. taken in by (larger) heterotrophic/host cell (through endocytosis);
c. new living arrangement mutually beneficial / depend on each other to exist as single organism;

b.

all the alleles/genes of a population (at a particular time)

c (ii).

Examiners report

While many candidates were able to get 1 mark, and some 2, few wrote clearly or accurately about the endosymbiotic theory. The question was not asking for evidence of the theory which is what some candidates wrote about.

b.

The definition of gene pool in (ii) was answered better than in previous years. 

c (ii).

Syllabus sections

Additional higher level » Topic 10: Genetics and evolution » 10.3 Gene pools and speciation
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